Methods for encapsulating waste and products thereof

ABSTRACT

A method for disposing of waste material employs an agglomerate formed by molding an admixture of waste material and thermosetting binder. The use of a thermoplastic resin sheet in conjunction with the agglomeration mold promotes the safety of the molding process. Dust and mold leakage is abated and it subsequently yields a resin coated agglomerate that is safe for handling. The performance of the agglomerate is enhanced by formation of a coating of resin chemically bonded onto its surface. The performance of the agglomerate may be further enhanced by the formation of a seam-free thermoplastic resin jacket over the resin coated agglomerate.

This is a divisional of copending application Ser. No. 08/097,295, filedon Jul. 26, 1993, now U.S. Pat. No. 5,401,452, issued Mar. 28, 1995, thecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The invention relates to solidification/stabilization of toxic wastematerial.

BACKGROUND ART

A process is described in U.S. Pat. No. 4,234,632 (Lubowitz) by thepresent inventor for the fabrication of waste forms by molding withmatch dye molds. Toxic material is mixed with thermosetting resin andthe mixture is charged into an agglomeration mold where it is confinedand subjected to heat to form an agglomerate. The free standingagglomerate placed in a second mold is then covered by powdered and/orpelletized thermoplastic resin and consolidated therein by heating andsolidified by cooling thereby resin jacketing the agglomerate on the topand sides. The partially encapsulated agglomerate is then inverted inthe mold. The untreated bottom of the agglomerate is covered withadditional thermoplastic resin that is heated and solidified. During theheating and solidification of the resin, it fuses with that on the rimof the preformed jacket to complete resin encapsulation of theagglomerate.

A commercially viable full scale production apparatus and method forpracticing the process of the above described patent for treatinghazardous wastes is described in U.S. Pat. No. 4,756,681 (Unger-1), U.S.Pat. No. 4,859,395 (Unger-2), and U.S. Pat. No. 4,932,853 (Unger-3) allby the present inventor, Unger, and Telles. These patents describe athree stage mold and a method for using same. In the first of threestages, a large volume of waste material is admixed with a thermosettingresin and transferred to an agglomeration mold. The moldable admixtureof waste material and thermosetting resin is confined therein andtransformed into a dimensionally stable agglomerate by the applicationof heat. The free standing agglomerate is then enveloped in the secondstage by a jacketing mold, and submerged by thermoplastic resin, aspowder and/or pellets, added in the space between agglomerate andjacketing mold and to the top of the agglomerate. After the applicationof heat and moderate pressure, a jacket of thermoplastic resinapproximately 6 mm. ( 1/4 inch) thick, fused onto the sides and top ofthe agglomerate, forms upon cooling the mold. In the third stage, thepartially, encapsulated agglomerate and mold are inverted together.Additional powder and/or pellets is added and fused onto the formerbottom of the agglomerate and to the rim of the preformed jacket to forma fully jacketed agglomerate. Once complete, the waste form exhibitsseamless resin encapsulation of the agglomerate. Inversion ofagglomerate and mold together, allowed by the equipment and the method,significantly advances large scale management of hazardous wastes. Alarge volume of hazardous waste is encapsulated by protectivethermoplastic resin. The seam free jacket of thermoplastic resin fusedupon the surface of the agglomerate gives rise to waste forms thatwithstand severe stresses of transportation, leaching stresses andphysical stresses, such as freeze-thaw and wet-dry, that may occur in alandfill. Additional references with respect to this process arechapters of two books: "Surface Encapsulation Process for StabilizingIntractable Contaminants", by Unger, Telles and Lubowitz (the presentinventor), pp. 40-52, Environmental Aspects of Stabilization andSolidification of Hazardous and Radioactive Wastes,©1989, ASTM STP 1033,Pierre Cote and Michael Gilliam, editors; and "EPP Process forStabilization/Solidification of Contaminants" by Unger and Lubowitz (thepresent inventor), pp. 77-86, Physical/Chemical Processes, InnovativeHazardous Waste Treatment Technology Series,©1990, Volume 2, TechnomicPublishing Co., Inc., edited by Harry M. Freeman.

Other methods of waste management entail surface treatment ofagglomerates, such as spraying or dipping of the agglomerate in asuitable coating material such as asphaltum or wrapping in a wire mesh,as disclosed in U.S. Pat. No. 3,330,088. Alternatively, the agglomeratedwastes may be wrapped in a vinyl sheet as disclosed in U.S. Pat. No.3,451,185. The large scale processes described in these two patents maybe suitable for the management of general refuse but they are notsuitable for achieving high performance management of low energyradioactive wastes and industrial hazardous wastes. The art described byUnger 1, 2 and 3, in contrast, yields processing advantages, and wasteforms that secure contaminants under harsh environmental stresses ofwaste management due to leaching, overburden, alternative wet and dryconditions, alternative freezing and thawing conditions, and mechanicalimpact.

The use of polyethylene for management of contaminated ion exchangeresin particulates and of evaporator concentrates is disclosed byNorboru et al. in Nuclear and Chemical Waste Management©1982, Vol. 3,pp. 23-28 and 131-137. Norboru discloses that polyethylene is a superiorbinder for this purpose. But waste forms resulting in the above art holdlow concentration of wastes due to the difficulty of effectivelyblending high concentrations into polyethylene resin.

Other methods of disposing of wastes include confining them in plasticor metal containers, or mixing wastes with binder materials such asaqueous cements and resins, and solidifying mixtures of wastes andbinder in the containers. All of these methods have significantdisadvantages. Both plastic and metal containers require prefabricationprior to waste management and thus they entail transporting appreciableunoccupied volume, and in addition, have a high relative initial cost.Containers are also subject to such problems as ineffective sealing andcorrosion which eventually allows leaching and seepage of the contents.Even the combination of confining waste and binder mixtures incontainers does not assure effective waste stabilization due to theshortcomings of containers.

None of the above techniques address the issue of dust and/or leakage ofcontainments during the process of confining or securing toxicmaterials. Due to the nature of the techniques, workers practicing theabove waste management processes need appreciable provisions forprotection against contamination by such wastes. Waste materials mayescape by dust formation, leakage, fragmentation, etc. Consequently, aneed exists for improved techniques for abating the contamination ofwork places in the management of toxic waste and for fabricating highperformance waste forms.

SUMMARY OF THE INVENTION

The present invention is directed to methods for encapsulating wastematerials which are cost effective and which enhance the safety ofinvolved personnel. In particular, methods in accordance with theinvention are realized with simple, inexpensive molds and materialswhich reduce dust and leakage typically involved in the handling andpackaging of waste and contaminants. The methods permit relaxation ofthe fabrication tolerances typically required in waste encapsulatingmolds. The life of the molds is lengthened by the reduction in exposureto corrosive wastes. Exposure of personnel to toxic materials duringencapsulation is also reduced by the controlled handling of the waste.Exposure after encapsulation is reduced by the durability of theresulting product. The invention also includes products produced usingthe methods.

Methods in accordance with the invention are characterized by the stepsof mixing waste material with a thermosetting binder to form anadmixture thereof, enclosing the admixture in thermoplastic sheetmaterial and applying heat and pressure to the admixture and theenclosing sheet to transform them respectively into a rigid agglomeratehaving an outer coat of fused resin.

In a preferred method embodiment, the enclosing step includes the stepsof providing an open top mold, lining the mold with a pouch of thethermoplastic sheet material, and pouring the admixture into the pouch.The applying step includes the steps of abutting the pouch with a moldtop and applying pressure to the mold top.

In another preferred method embodiment, an upper portion of the pouch ofthermoplastic material is formed into a sleeve and the admixture isdirected into the sleeve with a chute. In yet another preferred methodembodiment, at least a portion of the air within the pouch is removedprior to the pouring step.

In a preferred method embodiment, the thermosetting binder is comprisedof atactic 1,2-polybutadiene, the thermoplastic sheet material iscomprised of polyethylene, and the applied heat is between 79° C. and191° C. (200° F. and 400° F).

In another preferred method embodiment, the admixture is augmented withpolyfunctional epoxides, post-consumer polymers and glass fabric.

In another preferred method embodiment, a coating of thermosettingpolyester--chopped glass fiber is substituted for the thermoplasticsheet material.

Methods in accordance with the invention are further characterized bythe steps of surrounding the fused sheet resin coat with particulatethermoplastic resin and subjecting it to heat and pressure to form anouter jacket of fused particulate resin over the fused sheet resin coat.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will be best understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-14 illustrate preferred method and apparatus embodiments, inaccordance with the present invention, wherein:

FIG. 1 is a sectional view of an empty agglomeration mold;

FIG. 2 illustrates a pouch within the mold of FIG. 1;

FIG. 3 illustrates a pouch within the mold of FIG. 1 wherein the pouchdefines an upward extending sleeve to receive a loading chute;

FIG. 4A shows an admixture of waste material and thermosetting binderloaded into the pouch of either FIG. 2 or FIG. 3;

FIG. 4B shows a lining of glass fabric between the admixture and pouchof FIG. 4A;

FIG. 4C shows, in the mold of FIG. 1, thermosetting polyester--choppedglass fiber surrounding an admixture of waste material;

FIG. 5 illustrates a mold top compressing the admixture and pouch ofFIG. 4A;

FIG. 6 illustrates a resin coated waste agglomerate resulting from theapplication of pressure and additional heat during the step shown inFIG. 5;

FIG. 7 illustrates the resin coated agglomerate and mold base of FIG. 6within a jacketing mold;

FIG. 8 shows the resin coated rigid agglomerate of FIG. 7 submerged inthermoplastic resin particulates;

FIG. 9 shows a mold top compressing the resin coated rigid agglomerateand thermoplastic resin particulates of FIG. 8 and application of heat;

FIG. 10 illustrates inversion of the jacketing mold of FIG. 9;

FIG. 11 illustrates the inverted jacketing mold with the former moldbase removed;

FIG. 12 shows the resin coated rigid agglomerate of FIG. 11 covered bymore thermoplastic resin particulates;

FIG. 13 shows a mold top compressing the mold contents of FIG. 12 andapplication of heat; and,

FIG. 14 illustrates a jacketed resin coated agglomerate resulting fromthe application of pressure and additional heat during the step shown inFIG. 13.

MODES FOR CARRYING OUT THE INVENTION

The following cases exemplify the benefits of the invention: Forfabrication of agglomerates of toxic wastes stemming from an admixtureof binder resin and particulated toxic wastes, such as particles ofheavy metal wastes and/or those of ion exchange materials holdinglow-energy radioactive contaminants that stem from treating aqueouswaste streams from nuclear plants with ion-exchange resins and/orinorganic substances, a useful, simple agglomeration mold consists of apipe-like steel sleeve resting upon a steel, stepped platform. Uponheating the admixture in this mold, in certain cases, admixture maymigrate onto the platform from the interface of the sleeve and theplatform. One method for correcting this problem is to cause an intimatecontact of sleeve and platform by precision matching of the moldcomponents, and another, by placement of gaskets and/or sealant in theinterface area. But such methods may incur additional costs regardingmolds and processing, and these costs may impede commercial acceptance.A simple, low cost method is required to correct the problem. And thisis addressed by lining the agglomerate mold with polyethylene sheetforming a pouch prior to placement of the toxic waste admixture into themold.

The retention of the toxic admixture in the mold occurs as follows: Uponheating the mold, the polyethylene sheet undergoes softening, andtherewith "pleats" occurring in lining the polyethylene sheet into themold are "ironed out" due to compression of the sheet onto the innerwalls of the sleeve and the surface of the platform by the appliedweight of the toxic consignment, which is simultaneously hardening.Thereby plastic sheet material simultaneously seals the mold andsmoothly coats the agglomerate. Although the sheet softens, it yetprevents delocalization of toxic consignment at mold interfaces due toits high melt strength. With cooling of the mold, the sheet solidifies.The result is a significantly toughened agglomerate due to itsencapsulation by tough polyethylene sheet material adhering to itssurface. The sheet provides additional benefit by provision of an inertbarrier between agglomerate and personnel.

The benefit of the plastic pouch applies to agglomeration molds withgreater metal interface area than those of pipe-like sleeves. Thus a"split mold" whereby a sleeve is formed by tongue and groove pairing ofa sectioned metal cylinder may be employed notwithstanding itsadditional interface area. Such molds are useful in the practice of thisinvention because they may facilitate demolding of toxic wasteagglomerates, and they eliminate the need for overhead lifting apparatusrequired for demolding waste agglomerates from a pipe-like sleeve. Inaddition, rectangular molds with joined steel plates are employable.Conservation of space for waste storage may favor rectangular productsover cylindrical products.

Further treatment of the resin coated agglomerate by thermoplastic resinsuch as polyethylene encapsulates it by a seam-free resin jacket, about6 to 10 mm. (1/4 to 3/8 inch) thick. Polyethylene resin "flash"resulting in the encapsulating operation does not constitute a safety orenvironmental hazard because, in contrast to the admixture, thismaterial is non-toxic. The resin flash can be recaptured and powderedand/or pelletized for further use in the invention. Due to the toughnessof the free-standing resin coated agglomerates, thermoplastic recycleresin rather than virgin resin may be employed in fabricating wasteforms with high performance, thereby giving rise to its usefulemployment, reducing resin costs for waste forms and facilitatingrecycle resin disposal.

An apparatus for practicing the process of the present invention isdescribed in U.S. Pat. No. 4,756,681 (Unger-1), U.S. Pat. No. 4,859,395(Unger-2), and U.S. Pat. No. 4,932,853 (Unger-3), incorporated herein byreference. These patents describe a three stage mold and a method forusing same. The first stage of the Unger apparatus employs anagglomeration mold.

In the present invention, the agglomeration mold is fitted with aplastic lining of thermoplastic sheet resin, preferably of polyethyleneresin sheet stock. Other resin sheets are also employable, e.g.,polyester, polyolefin, polyamide, polyvinylidene fluoride,polyvinylidene chlorides, as alternative preferred compositions for moldlining. Multiple resin sheets are employable for making a thicker moldlining and thicker resin coating of resulting agglomerates. Thethermoplastic sheet lines the cavity of the agglomeration mold so as toform a pouch therein. When toxic material is loaded into theagglomeration mold, it is confined within the pouch. The pouch serves toabate emission of contaminates from the agglomeration mold inagglomerate formation. Without the pouch, toxic material can leakthrough worn or low tolerance sealing surfaces of the mold.

Accordingly, use of the pouch can relax the tolerances required whenmachining the agglomeration mold, i.e. the precision of the machiningprocess is relaxed. Relaxing the standard of precision for machining themold reduces the cost of such machining.

Further cost savings are realized by use of the pouches due to theenhanced life expectancy of the agglomeration mold. The life expectancyof the mold is enhanced because the pouch prevents or reduces theintrusion of waste particles onto the surfaces and interfaces of themold cavity. Absence or reduced presence of waste particles at moldsurfaces and interfaces diminishes metal corrosion and the rate of wearof mold tolerances.

In an embodiment of the apparatus, a chute is employed for directingtoxic material into the pouch. In an embodiment of the method, the pouchis extended as a pipe or sleeve toward and connected with the exit spoutof the chute. The connection between the chute and the pouch helps toabate the emission of dust or particulate material during the transferprocess. Furthermore, if the pouch forms a closed system with the chute,i.e. the only access to or from the pouch is through its connection withthe chute, and if the pouch remains substantially deflated with respectto air, then, when material is charged into the pouch through the pouchsleeve, very little air is displaced therefrom. Instead, as the pouch isfilled with material, it displaces air from the cavity of theagglomeration mold. The presence of the pouch prevents contact betweenthe air in the mold and the material being charged into the pouch.Accordingly, as air is discharged from the agglomeration mold by theexpanding pouch, it does not contact the waste material being chargedtherein and does not generate dust formation. Accordingly, the pouch canserve to prevent or abate the generation and emission of air born dust.

After the pouch is positioned within the cavity of the agglomerationmold and/or connected to a spout, it is then filled or charged with amoldable admixture of waste material and a thermosetting resin binder.The thermosetting binder is of a type which can form a consolidatedagglomerate with the waste material upon the application of heat. Theresultant consolidated agglomerate has a rigid structure. Preferredthermosetting binders as described in U.S. Pat. No. 4,234,632 may beutilized, the disclosure of which is hereby incorporated by referenceand made a part hereof. Atactic 1,2-polybutadiene with a molecularweight of about 3000 is a preferred thermosetting resin binder.

Low molecular weight binders are preferred because of their greaterfluidity. A high level of fluidity is useful when blending highconcentrations of waste with binder prior to agglomeration. On the otherhand, excessive fluidity due to the use of low molecular weight bindersmay give rise, in some cases, to resin drainage in the agglomerationmold during heating, thereby circumventing desirable uniformdistribution of resin within the agglomerate. Drainage depletes resinfrom the top of the agglomerate and enriches the bottom with anexcessive proportion. To prevent this occurrence, polybutadiene resinfitted with chemically functional groups and combined with coreactants,such chemical compositions reacting at temperatures above roomtemperature but below that needed for chemical thermosetting of thebinder, causes formation of a viscous or gel state at moderatetemperatures which inhibits binder migration at the elevatedtemperatures needed for 1,2-polybutadiene binder thermosetting.Preferred compositions are those of carboxyl terminated atactic1,2-polybutadiene and polyfunctional epoxides. Unrefined polybutadieneresin and epoxides are employable for making agglomerates thus reducingcosts for thermosetting binders.

The moldable admixture may also include a supplemental component ofthermoplastic binders. Post-consumer polyethylene, nylon, polypropylene,and polyester may also be employed as supplemental components of thebinder resin. Such resins are generally considered unsuitable forinjection molding and blow molding due to their unpredictablerheological properties. However, as supplemental components of amoldable admixture processed in the heated agglomeration mold, therheological properties of recycle resin do not materially affectproperties of the fabricated agglomerate. Since these materials may beless costly than polybutadiene, their utilization in conjunction withpolybutadiene may further reduce cost of agglomerate fabrication.

The toxic waste may be either particulate or mixed with water in theform of an aqueous sludge. Sludges are solidified prior to agglomerateformation. Cementious materials such as portland cement may be employedto solidify aqueous sludges into friable monolithic material andsubsequently particulated. Oil containing sludges may be managedlikewise by clay materials in conjunction with aqueous cements. Examplesof particulate wastes suitable for treatment in this process includethose holding heavy metal contaminants such as arsenic, lead, mercury,and radioactive materials. After thorough blending, the polybutadieneresin treated particulate wastes may be free flowing particulates. Inall cases, the mixtures are stable under atmospheric conditions, thuspermitting their subsequent agglomeration to be scheduled as desired. Anexample of a sludge suitable for treatment is one holding PCB's.

As a result of heating, the mixtures consolidate by the polybutadieneundergoing chemical thermosetting thereby creating a rigid matrix forthe toxic waste. Thermosetting is initiated by peroxides such asemployed in the peroxide vulcanization of rubber. The 1,2,-configurationpolybutadiene gives a high yield of chemical cross-links in a fastchemical reaction. In the course of heating and reaction, recyclepolyethylene particulates within the blend are chemically incorporatedinto the polybutadiene. The resulting rigid resin matrix has singlybonded carbon, chemically cross-link configurations which provideinherent resistance to matrix degradation by oxidation, hydrolysis,radiation, and permeation by water and solvents. Once the thermosettingof the polybutadiene has occurred, reheating does not remelt the toxicwaste agglomerate.

The pouch also participates in the thermosetting process which occursduring heating of the toxic waste admixture in the mold. When the pouchin the cavity of the agglomeration mold is charged with the moldableadmixture, it may pleat therein, due to weight and conformation of thedeposited material to the mold cavity. However with the application ofheat, the pleated pouch will conform to the inner walls of the mold andthus form a smooth coating on the agglomerate surface. There are twoelements of such integration, viz.:

1. The pouch material will undergo fusion and will mate withpolybutadiene binder at the surface of the agglomerate, and

2. The thermosetting binder will chemically cross link with the pouchresin so as to form chemical bonding between the pouch and the wasteagglomerate.

When heated, the thermoplastic composition of the pouch thus softens andadheres to the surface of the waste agglomerate. Due to its highviscosity in the softened state and due to its proximity to the surfaceof the mold cavity, the pouch material will tend not to migrate withinthe cavity and will tend to remain at the surface. Chemical crosslinking occurs between the 1,2,-configuration polybutadiene and thepolyethylene sheet material of the pouch in the heated mold and thisfurther tends to hold the pouch in place. Accordingly, at the conclusionof heating and with cooling, the surface of the resulting wasteagglomerate will be resin coated and encapsulated by the pouch resin.This coat forms a seal of polyethylene resin onto contaminates on thesurface of the agglomerate and prevents their contact with personnel andequipment. It also significantly advances the toughness of theagglomerate.

The coating of a waste agglomerate with a sheet of thermoplasticmaterial significantly enhances the performance of the agglomerate ascompared to that of uncoated agglomerates. Coated agglomerates exhibitenhanced safety during fabrication, handling and disposal due to itsadvanced physical and mechanical properties over those of uncoatedagglomerates. These advantages are optimized by chemical adhesion of thethermoplastic material at the agglomerate surface with the agglomeratebinder. The high strength of adhesion stems from chemical forces at theinterface by virtue of covalent bonding as well as polar, van-der-waal,and dispersion phenomena.

The strength of the bond formation between the agglomerate and itsthermoplastic coating may be optimized by use of the 1,2-polybutadieneas the resin binder for agglomerate formation in conjunction with theuse of a pouch having a composition of polyethylene resin. Thiscombination is cost effective and yields optimal chemical bonding at theinterface of agglomerate and coating. During agglomerate formation,binder resin wets both waste particles and the polyethylene resin pouchdue to favorable surface energetics. Agglomerate formation occurs byhomopolymerization of polybutadiene. Polymerization is enhanced byincorporation of free radical formation catalysts into the polybutadieneresin, e.g., known peroxide catalysts used in rubber vulcanization. Thepreferred temperature range for agglomerate formation is between 79° C.and 191° C. (200° F. and 400° F.). As the agglomerate is heated fromambient temperature to the preferred temperature range, binder wettingof the pouch resin is enhanced due to some binder impregnation at thehigher temperature, thereby enhancing free radical interaction of thebinder and the pouch.

Free radical polybutadiene polymerization is the phenomenon that causesformation of rigid agglomerates of toxic wastes. In the case of1,2-polybutadiene, in contrast to 1,4-polybutadienes, catalysts cause agreater amount of the resin unsaturation to be chemically consumed, thusenhancing agglomerate rigidity. In the presence of the polyethylenepouch, it is postulated that the electron bearing polybutadiene canextract from the polyethylene resin a hydrogen atom which terminates thepropagation reaction of the polybutadiene. However, an electrontransferred to the polyethylene resin initiates further polybutadienepolymerization, thereby causing chemical linkage between polybutadieneand polyethylene. Chemically enhanced adhesion of the binder and thecoating, as stated previously, advances performance of agglomerates oftoxic wastes.

Accordingly, performance of the coated waste agglomerate is superior touncoated waste agglomerates because the presence of the coat tends toprevent or abate the following processes, viz.:

1. Particles of contaminant are less likely to be displaced from thesurface of waste agglomerates due to contact by personnel and equipment;and

2. Chipping or fragmentation of the surface of the waste agglomerate dueto mishaps during handling is abated by the presence of the fused coat.

In another preferred embodiment, the agglomerate may be furtherstrengthened by the addition of glass fibers to the admixture of toxicmaterial and binder thereby toughening the agglomerate. Alternatively,when formation of appreciably toughened agglomerates are required glassmat or glass fabric may be employed. After the cavity of theagglomeration mold has been draped by thermoplastic sheet material toform a pouch therein, a glass fabric disc may be placed in the pouch sothat it rests on the bottom of the mold and then glass fabric in theform of a scroll is inserted into the pouch and onto the disc, andunravels to press the pouch against the cavity. An admixture of wastematerial and binder "snugs" the plastic sheet and glass fabric againstthe mold walls by its weight. A glass fabric disc is then place atop theadmixture and the thermoplastic resin pouch is then folded thereon.During the curing process, binder material within the admixture wets andpenetrates the glass fabric and contacts the thermoplastic sheetmaterial. In the final cure state, the glass fabric and the pouch arebonded together upon chemical bond formation between pouch resin andbinder resin thus advancing appreciably the mechanical strength of theresin coated agglomerate.

As a further preferred embodiment, the agglomerate may be mechanicallystrengthened by spraying the cavity of the agglomeration mold with athermosetting polyester-chopped glass fiber mixture so as to form aglass reinforced resin sheet coated thereon. Some commercialcompositions harden at atmospheric temperatures. The admixture of wastematerial and thermosetting binder is then transferred into the coatedmold. Once the transfer is complete, the top of the admixture is sprayedwith polyester-chopped glass. Provision is made for this top material tocontact at the edge with that sprayed previously so as to encapsulatethe admixture therein. When the ensemble is heated, the admixtureconsolidates to form an agglomerate. The resulting product obtained upondemolding is a free standing agglomerate coated by glass-fiberreinforced resin. Alternatively, waste materials may be made freestanding without need for waste hardening due to the rigid nature of theglass fiber reinforced resin coating. Such ensembles are suitable forfurther treatment by encapsulation with thermoplastic resin. The bindermay therefore be omitted when encapsulating these types of wastematerials.

The following is a diagrammatic description of resin coated agglomerateand waste form fabrication.

FIGS. 1 through 5 illustrate the first stage in the molding processwhich provides a means for molding the first moldable material to createthe rigid agglomerate. FIG. 1 is the first step in the process and showsa sectional view of an empty agglomeration mold 10 combined with a base11. A preferred agglomeration mold has a sleeve configuration. However,agglomeration molds having a split configuration or a "clam"configuration may also be employed. Such molds are simple and facilitatethe demolding process by eliminating the need for overhead gear neededto free the agglomerate from the sleeve. In the preferred embodiment,the agglomeration mold 10 is cylindrical and the base 11 is circular. Astep 12 in the bottom of the agglomeration mold 10 provides vertical andhorizontal registration of the agglomeration mold 10 on the base 11. Theinner diameter of the mold 10 represented by the arrow 13 determines theouter diameter of the agglomerate.

FIG. 2 illustrates the insertion into the cavity of the agglomerationmold of a pouch 14 having a composition of thermoplastic sheet material.In this instance, the thermoplastic sheet material is merely draped overthe cavity of the agglomeration mold.

FIG. 3 illustrates a modified pouch 15 having a sleeve or pipe 16 whichis extended to connect with the exit of a chute 17. The pouch can bedeflated and inserted within the cavity of the agglomeration mold. Whenmaterial is passed through the chute, it is collected within the pouch.

FIG. 4A illustrates a moldable admixture 18 transferred into the pouch14 (or 15) within the cavity of the agglomeration mold. After thetransfer is complete, the upper portion of the pouch is disconnectedfrom the chute and folded atop the moldable admixture.

FIG. 4B illustrates an alternative method embodiment in which the stepssummarized in FIG. 4A are augmented by a lining of glass fabric disposedbetween the pouch 14 and admixture 18 of FIG. 4A.

Prior to transferring the admixture 18 into the pouch 14, a glass fabricdisc 20A is placed in the bottom of the pouch 14 and then a scroll 20Bof glass fabric is inserted to line the walls of the pouch 14. Aftertransferring the admixture 18 but prior to folding the upper pouchportion 19 thereon, another glass fabric disc 20A is placed over theadmixture 18 (the discs 20A and scroll 20B are indicated by broken linesfor clarity of illustration).

FIG. 4C illustrates another preferred method embodiment in which thesteps summarized in FIG. 4A are replaced by coating the interior of themold 10 and base 11 with a thermosetting polyester--chopped glass fiber21. The admixture 18 is then transferred into the mold 10. Additionalthermosetting polyester--chopped glass fiber is then sprayed over thetop of the admixture 18 (the lining 21 is indicated by broken lines forclarity of illustration).

Any of the preferred methods of FIGS. 4A, 4B, and 4C may be practicedprior to the steps shown in FIG. 5 which is a sectional view similar toFIG. 4A with a rigid top 22 positioned inside the agglomeration mold 10to apply pressure to compress the mixture 18 and eliminate any voids. Ashaft 24 connected to a piston provides a first compression means toforce the top 22 down and heat is applied causing the polybutadiene tothermoset creating a rigid agglomerate 26 of the mixture 18. Completecuring occurs when the center of the mixture 18 reaches approximately135° C. (300° F.). Cure times are dependent upon the proportion of thewaste material, the proportion of polybutadiene, the shape of the mold,the heat of the mold, and the bulk of the mixture 18. In the preferredembodiment, a preferred volume of the admixture is between 38 and 380liters (approximately 10-100 gallons) and a most preferred volume is 163liters (approximately 43 gallons). In a preferred mode, the rate ofproduction of waste agglomerates is enhanced by placing several chargedagglomeration molds in a large oven at one time.

An alternative method is also available for the method shown in FIG. 4C.Waste materials may be rendered free standing without addition of binderresin due to the rigid nature of the glass fiber reinforced resincoating. The binder may therefore be omitted when fail safe criteria canbe somewhat relaxed in the final product. The time required to completethe molding process is significantly reduced as the entire mass does notneed to be heated.

FIG. 6 is a sectional view of the agglomerate 26 sitting on the base 11after removal of the agglomeration mold 10 and the mold top 22 shown inFIG. 5. Shrinkage of the agglomerate 26 away from the agglomeration mold10 occurs as the agglomerate 26 cools facilitating the removal of themold 10. The resultant rigid agglomerate is sealed with an outer coat 27of fused resin from the thermoplastic sheet material of the pouch in thecase of the method illustrated in FIG. 4A, a thin layer of fusedthermoplastic sheet material and glass fabric in the case of the methodillustrated in FIG. 4B, or a thin layer of thermosettingpolyester--chopped fiber in the case of the method illustrated in FIG.4C.

In a preferred embodiment, the performance of the resultant coated wasteagglomerate may be further enhanced by transferring the resin coatedwaste agglomerate to a jacketing mold. The coated waste agglomerate isjacketed therein with thermoplastic resin, preferably polyethyleneresin. The thermoplastic resin employed to encapsulate the rigidagglomerate may be powdered, pelletized, and/or reground, hereinafterreferred to as "particulate", and is preferably high density or linearlow density polyethylene. The jacketing mold employed provides a gap tothe surface of the agglomerate. The gap is filled with the particulatepolyethylene. Upon heating and cooling, the polyethylene forms a toughjacket that is adhesively and chemically bonded to the surface of theagglomerate. Polyethylene is a thermoplastic that melts on reheating.The remelting of a portion of the plastic jacket is useful in the methodof the present invention because it allows particulate polyethylene tobe added at a later stage of the encapsulation process. In this laterstage, the added resin melts and fuses with the previously moldedparticulate polyethylene to complete the seamless encapsulation of theagglomerate. The jacket thickness is determined by the dimension of thegap provided by the jacketing mold. A preferred range of this gap isbetween 2 mm. and 2.5 cm. (approximately 1/16 and 1 inch) with a mostpreferred gap of 1 cm. (approximately 3/8 inch).

The resultant jacketed waste agglomerate is then demolded to yield aseamless encapsulation of such agglomerates. The resulting jacketedagglomerates can withstand the stresses of handing and transportationand exhibit enhanced long term immobility of their content in finaldisposal in the earth. The process for jacketing coated wasteagglomerates is similar to the process for jacketing uncoated wasteagglomerates as taught by Unger (supra).

The jacketing process is enhanced by the formation of the chemicallybonded coat of polyethylene on the surface of an agglomerate. Thepolyethylene interlayer bridges the thick polyethylene jacket to theagglomerate surface by means of strong chemical bonding, i.e. thepolyethylene coat is chemically bonded to the agglomerate surface and isfused to the polyethylene jacket. Jacketing without a coating ofchemically bonded polyethylene relies upon mechanical forces andnon-covalent bond adhesion between the two layers.

FIGS. 6 through 14 illustrate the jacketing process. FIG. 6 illustratesa resin coated rigid agglomerate 26 demolded from the agglomeration moldand sitting on the base 11. FIG. 7 is a sectional view similar to FIG. 6with a jacketing mold 28 combined with the base 11. The jacketing mold28 is also cylindrical. The horizontal registration for the jacketingmold 28 on the base 11 is determined by the diameter of the base 11. Thejacketing mold 28 creates a gap 32 between the sides 34 of theagglomerate 26 and the inner surface 36 of the jacketing mold 28 formolding a second moldable material such as particulate polyethylenearound the sides 34. FIG. 8 is a sectional view similar to FIG. 7 withparticulate polyethylene 38 poured over the top 40 of the agglomerate 26and into the gap 32 to load the base 11 and the jacketing mold 28. Thedepth of the particulate polyethylene over the top 40 is adjusted to beapproximately equal to the predetermined thickness provided by the gap32. The bottom 42 of the agglomerate 26 remains sitting on the base 11.

FIG. 9 is a sectional view similar to FIG. 8 with a base 11' on top ofthe polyethylene 38. The base 11' is identical to the base 11 allowinginterchange. A second compression means represented by a shaft 46presses the base 11' of the jacketing mold onto the polyethylene 38. Theparticulate polyethylene 38 is then heated to melt and consolidate thepolyethylene 38. The polyethylene 38 is cooled to form a jacket 48 onthe sides 34 and the top 40 of the agglomerate 26.

FIGS. 10 through 14 illustrate the second portion of the jacket moldingprocess which provides for inverting the partially jacketed agglomerate26 and a means for molding the second moldable material on the formerbottom 42 to jacket the former bottom 42 of the agglomerate 26 andcomplete the seamless encapsulation of the agglomerate 26. FIG. 10 is asectional view similar to FIG. 9 with the shaft 46 removed and thepartially jacketed agglomerate 26, jacketing mold 28, and bases 11 and11' being inverted as indicated by the arrows 50.

FIG. 11 shows the view of FIG. 9 inverted 180° with the base 11 andshaft 46 removed exposing the unjacketed former bottom 42 of theagglomerate 26.

FIG. 12 is a sectional view similar to FIG. 11 with particulatepolyethylene 38' loaded over the former bottom 42 of the agglomerate 26and the jacket 48 adjacent the former bottom 42 to a depth approximatelyequal to the gap 32 of FIG. 7.

FIG. 13 is a sectional view similar to FIG. 12 with the base 11 replacedin the jacketing mold 28 to abut the added particulate polyethylene 38'.The base 11 is under compression from the shaft 46 to create sufficientpressure to mold the added particulate polyethylene 38'. Both the newlyadded polyethylene 38' and the adjacent polyethylene jacket 48 are thenheated. Upon heating both polyethylene components melt and fuse to oneanother. Upon cooling, the fused components of polyethylene form aseamless jacket 50 shown in FIG. 14 to complete the encapsulation of theagglomerate 26. As noted above, the remelting of a portion ofpolyethylene jacket 48 on the sides 34 is useful in the method of thepresent invention because it allows the former bottom 42 to be jacketedat this later stage and fuse with the previously molded jacket 48 on thesides 34 producing a seamless encapsulation of the agglomerate 26. Inaddition, the melting of the particulate polyethylene also remelts theouter coat 27 (FIG. 6) of fused resin from the thermoplastic sheetmaterial fusing all of the thermoplastic resin together.

FIG. 14 illustrates jacketed waste agglomerate 26 jacketed with theseamless jacket 50 demolded and sitting on the mold base.

The embodiments depicted herein are exemplary and numerous modificationsand rearrangements can be made with the equivalent result still embracedwithin the scope of the invention.

What is claimed is:
 1. A resin encapsulated waste agglomerate,comprising:a substantially rigid agglomerate formed by mixing wastematerial with a thermosetting binder and subjecting the mixture to heatand pressure; an agglomerate enclosing coat of resin formed from athermoplastic sheet fused to said agglomerate by application of heat andpressure; and, an enclosing jacket of resin formed from a thermoplasticparticulate resin approximately one centimeter thick fused to said coatby application of heat and pressure.
 2. The encapsulated agglomerate ofclaim 1 wherein said thermosetting binder comprises atactic1,2-polybutadiene.
 3. A resin encapsulated waste agglomerate,comprising:a substantially rigid agglomerate formed by mixing wastematerial with a thermosetting binder and subjecting the mixture to heatand pressure; an agglomerate enclosing coat of resin formed from athermoplastic sheet fused to said agglomerate by application of heat andpressure; and, an enclosing jacket of resin formed from a thermoplasticparticulate resin approximately two millimeters to two and one-halfcentimeters thick fused to said coat by application of heat andpressure.
 4. The encapsulated agglomerate of claim 3 wherein saidthermosetting binder comprises atactic 1,2-polybutadiene.